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Today’s Practice: Heart Failure
Interventional
Heart Failure
A new clinical subspecialty emerges.
By Navin K. Kapur, MD, FSCAI, FACC
H
eart disease remains the number one cause of
mortality in the United States.1 During the past
50 years, pharmacologic advancements for cardiovascular risk factors and device innovation
for the management of coronary disease, including acute
myocardial infarction (AMI), have radically changed the
landscape of heart disease. No longer is AMI considered
a terminal event, as in-hospital mortality rates have been
reduced to less than 10%. As a result, more individuals
are now surviving their incident and subsequent heart
attacks. However, with each myocardial insult, nearly
25% of individuals develop chronic heart failure after an
AMI,2 leading to a virtual tsunami of patients with heart
failure now entering the catheterization laboratory.
A NEW DEMAND
An estimated 2.6% of the American population suffers from heart failure, which is defined as “a syndrome
caused by cardiac dysfunction, generally resulting from
myocardial muscle dysfunction or loss and characterized
by either LV dilation or hypertrophy or both.”3 The spectrum of heart failure can be broadly categorized into two
groups: acutely decompensated heart failure/cardiogenic
shock and chronic progressive heart failure. Regardless of
their clinical presentation, nearly all patients with heart
failure will pass through the catheterization laboratory at
some point in their clinical evaluation and management.
As a result, every interventional cardiologist encounters
patients with heart failure on a daily basis.
For this reason, the concept
of interventional heart failure
is less of a radical new subspecialty, but rather a response
to the increasing demand for
interventionists who are trained
in advanced invasive hemodynamics, can interface with an
advanced heart failure/mechanical support/cardiac transplant
program, and have experience
with emerging cutting-edge
technologies for the management of patients with heart
failure.
Part of the reason for this
growing demand for the interventional heart failure subspeFigure 1. Due to a shift in the target population for surgical left ventricular assist devices
cialist is that surgical innova(LVADs) away from end-stage to “less sick” patients, the modern-day interventional cardition has now created an exit
ologist may be asked to manage patients with severely advanced heart failure and cardiostrategy for patients who were
genic shock using percutaneous circulatory support devices as a bridge-to-decision option.
considered medically futile
(REMATCH OMM: Randomized Evaluation of Mechanical Assistance in Treatment of Chronic (Figure 1). Surgically implantHeart Failure Optimal Medical Management). Reprinted with permission from Miller LW.
ed, durable mechanical supLeft ventricular assist devices are underutilized. Circulation. 2011;123:1552–1558.
port devices were once large,
july/august 2013 cardiac interventions Today 21
Today’s Practice: Heart Failure
A
B
C
Figure 2. Cardiac effects of mechanical support. Illustrations of pressure-volume loops after treatment with intra-aortic balloon
pump counterpulsation (A), percutaneous LV assist devices (TandemHeart or Impella 5.0) (B), or venoarterial extracorporeal
membrane oxygenation (C). Shaded loop represents left ventricular stroke work and stroke volume after device activation.
bulky pulsatile pumps designed to temporarily bridge
a patient to cardiac transplantation for a few weeks or
months. In the modern era, miniaturized continuousflow ventricular assist devices are now demonstrating
nearly 75% 2-year survival rates with improved patient
functionality.4 As a result, the 70-year-old patient with
cardiogenic shock for whom medical treatment held
minimal promise, may now be a viable candidate for
advanced mechanical therapies. Given this option, interventional cardiologists are now being asked to adopt a
more aggressive approach to salvaging patients from cardiogenic shock with percutaneously delivered mechanical circulatory support systems.
ACUTE CIRCULATORY SUPPORT
In parallel to the growth of surgical devices, acute circulatory support devices have also evolved from pulsatile
systems to miniaturized, continuous-flow pumps. These
pumps, which include the intra-aortic balloon pump
(IABP), venoarterial extracorporeal membrane oxygenation
(VA-ECMO), a catheter-mounted axial-flow pump (Impella;
Abiomed Inc., Danvers, MA), and the pLA-FA centrifugal
bypass (TandemHeart; Cardiac Assist Inc., Pittsburgh, PA)
system are used primarily to support high-risk coronary
intervention in patients with advanced heart failure and
to sustain multiorgan perfusion, while reducing cardiac
workload in cardiogenic shock. Newer applications for these
devices include adjunct support for transcatheter aortic
balloon valvuloplasty and valve replacement, high-risk ventricular ablation, and right ventricular failure.
Each pump is associated with a unique hemodynamic signature (Figure 2). The well-established IABP displaces blood
volume from the descending aorta by inflating during diastole and deflating during systole. The net effect of an IABP
is to augment coronary blood flow while reducing native
22 cardiac interventions Today july/august 2013
left ventricular systolic pressure and increasing native stroke
volume. Major advantages of the IABP are ease of insertion,
rapid deployment, and global familiarity with the technology. Disadvantages of the IABP include a limited degree of
ventricular unloading and reduced pump function during
tachycardia.
In contrast to IABPs, rotodynamic pumps are nonpulsatile systems that transfer rotational kinetic energy into the
bloodstream and generate forward flow. The two primary
rotodynamic pumps used to unload the left ventricle in the
catheterization laboratory are the TandemHeart and the
Impella systems. An emerging axial flow catheter in development is the percutaneous heart pump (PHP; Thoratec
Inc., Pleasanton, CA). VA-ECMO is often used in cases
of respiratory failure or to stabilize patients with severe
hemodynamic instability who cannot be transported to the
catheterization laboratory. Importantly, VA-ECMO will not
effectively reduce left ventricular workload unless an accompanying pump is used, such as an IABP or Impella device.
Alternative venting strategies with VA-ECMO are actively
being explored.
The TandemHeart device is an extracorporeal centrifugal pump that uses two percutaneously delivered cannulas
to pump oxygenated blood from the left atrium to the
systemic circulation via the femoral artery. For left heart
support, the TandemHeart device requires a transseptal
puncture for delivery of the 21-F inflow cannula and a
separate arterial access site for a 15-, 17-, or 19-F arterial
cannula. Depending on the size of the outflow cannula,
directly measured flow through the device ranges from 3.5
to 5 L/min. The hemodynamic effect of the TandemHeart
device is to reduce left ventricular preload and thereby
decrease native ventricular volume and pressure. The net
effect is a significant reduction in left ventricular wall stress
and stroke work. Major advantages of the TandemHeart
Today’s Practice: Heart Failure
Figure 3. Percutaneous biventricular support.
pump are the magnitude of ventricular unloading without
the need for surgical vascular access and avoidance of penetration in the left ventricle, which is helpful in the cases
involving ventricular thrombus and aortic regurgitation.
Disadvantages of the device include the need for transseptal puncture, two vascular access sites, and the need for
an arterial cannula up to 19 F in size to achieve maximal
unloading.
The Impella pumps are axial-flow catheters that directly
displace blood from the left ventricle into the ascending
aorta. The devices can be placed via femoral arterial access
in retrograde fashion across the aortic valve into the left
ventricle. Three distinct catheters can be used for left ventricular support and include the 2.5 LP, the CP, and the 5.0
LP devices. Estimated flows achievable with each device are
2.5, 3.5, and 5 L/min, respectively. Both the 2.5 LP and the
CP device can be deployed via percutaneous arterial access,
whereas the 5.0 LP device requires surgical vascular access.
In contrast to the TandemHeart device, the Impella systems
can be deployed via surgical access through the axillary
artery, thereby providing ventricular support via a supradiaphragmatic approach and allowing for longer-term support
with improved patient mobilization. Major advantages of
the 2.5 LP and CP devices are ease of insertion, rapid deployment, and emerging familiarity with the devices in most
catheterization laboratories. The major disadvantage of
the Impella pumps is the need for surgical access to deploy
the 5.0 LP pump, which provides the greatest amount of
unloading among the Impella device options.
DISCUSSION
As experience with each device grows, catheteriza­tion
laboratories are identifying which devices work best for
them in various clinical scenarios, including high-risk coronary intervention, AMI complicated by cardiogenic shock,
acutely decompensated heart failure, and right heart failure.
One of the major issues in the field of temporary circulatory support is the apparent disconnect observed between
hemodynamic improvement and clinical outcomes in
patients with cardiogenic shock. Several possible reasons
may contribute to this observation and include (1) patient
selection, (2) device selection, (3) delays to device activation,
and (4) no viable exit strategy. Of these possibilities, delays
to device activation in patients with cardiogenic shock
refractory to medical therapy alone is a modifiable factor
that requires a better understanding of how these devices
work and better crosstalk among interventionists, heart failure specialists, and critical care teams.
For example, several studies have shown that activation of
either an IABP or catheter-mounted axial flow pump, such
as the Impella device, before coronary occlusion can reduce
myocardial infarct size in surgical models of AMI.5,6 More
recently, we reported the effects of reducing left ventricular
wall stress with the TandemHeart device in a porcine model
of acute myocardial infarction.7 In this study, device activation was followed by a 30-minute delay in coronary reperfusion, suggesting that first reducing ventricular wall stress may
be an approach to reduce myocardial damage in patients
with AMI.7
Based on these collective findings, the TRIS
(TandemHeart to Reduce Infarct Size) trial will evaluate the effectiveness of ventricular unloading on the
reduction of infarct size for patients who have had a
severe heart attack. If proven effective, several paradigms
could change. First, the concept of door-to-balloon may
instead refocus to now include “door-to-unload” as a
therapeutic approach in AMI. Second, the number of
patients surviving their initial heart attack who develop
chronic heart failure may be reduced, suggesting that
mechanical therapy is an approach to prevent the development of subsequent heart failure after a heart attack.
To date, however, translating preclinical studies of myocardial salvage into clinical benefits has remained elusive.
Another major advancement in the field of interventional heart failure has been the development of percutaneous strategies to address right heart failure. As more
patients develop chronic left heart failure, the importance
of right ventricular function has begun to take center
stage because reduced right ventricular function portends
a worse prognosis in AMI, cardiogenic shock, chronic
left heart failure, and pulmonary hypertension. Several
recent reports have examined the clinical utility of the
july/august 2013 cardiac interventions Today 23
Today’s Practice: Heart Failure
TandemHeart device as a right atrial-to-pulmonary arterial bypass system for right ventricular support and have
shown that early device activation may be associated
with better outcomes,8 and further, that concomitant left
ventricular failure is an important contributor to mortality
despite right ventricular support.9 With the recent launch
of the Impella RP system, the RECOVER RIGHT trial will
explore the clinical utility of a percutaneous, single-access
site approach to mechanically supporting the failing right
ventricle. Furthermore, developments in right ventricular
support technology now open the door to biventricular
support for severe cardiogenic shock (Figure 3).10
CONCLUSION
Heart failure was once considered a terminal diagnosis,
and management focused on symptom management,
palliation, and the rare opportunity for cardiac transplantation. With major advances in mechanical circulatory support technology, the light at the end of the tunnel
has become brighter for patients with advanced heart
failure. Given the growing number of patients with heart
failure and the therapeutic options available to them,
the next generation of interventional operators will be
asked to think like heart failure specialists. As a result,
the subspecialty of interventional heart failure is now an
expanding movement and an emerging reality. n
Navin K. Kapur, MD, FSCAI, FACC, is with the Division
of Cardiology, Tufts Medical Center
Molecular Cardiology
Research Institute in Boston, Massachusetts. He has disclosed that he received research support from Cardiac
Assist, Abiomed, Maquet, Heartware; is a consultant for
Thoratec; and receives speaker honoraria from Maquet.
Dr. Kapur may be reached at [email protected].
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Subcommittee. Executive summary: heart disease and stroke statistics—2012 update: a report from the American
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